PONE-D-21-27419SARS-CoV-2 induces a durable and antigen specific humoral immunity after asymptomatic to mild COVID-19 infectionPLOS ONE

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Reviewer #1: Partly

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: I Don't Know

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Reviewer #1: No

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: The authors previously published a similar study cited in reference 20 in September of 2020 showing health care workers (HCW) have a higher risk of contracting COVID-19. Here these authors essentially repeated the same serological assays and concluded quickly that this is a 4-month follow-up study to show anti-spike antibody titers were sustainable whereas anti-NP antibody titers were not.

I think the conclusion was very limited in the sense that this type of study reflected a research attitude of " salami slicing" which means that an tactic is used to provide fragmented data with a trade-off between quality and quantity of the researches. One may wonder that given the time frame now it has been more than one year since their previous report (ref 20) why these authors now report a follow-up study of only 4 months?

In addition, the conclusion brings in little new insight since nowadays more important question is to address cross-protection of antibody toward new emerging strains of virus of concern, such as delta variant and other questions alike.

Reviewer #2: The authors describe the serological responses to asymptomatic SARS-CoV-2 infection, indicating that, similar to symptomatic infection, antibodies against the S glycoprotein, including those with neutralising potential, remain at higher levels longer than antibodies against the nucleoprotein. Furthermore, the magnitude of antibody responses appeared to be lower in asymptomatic infection compared to symptomatic infection.

The objectives of the study are clearly described, the work is thorough, and the data are well well-described and support the conclusions drawn. Whilst these findings are not entirely novel, they do increase understanding of humoral responses in mild/asymptomatic infection. The authors do well to highlight that the asymptomatic and symptomatic cohorts differ widely, and so no direct comparisons can be made.

I like this study in its present form and have only a few minor suggestions.

1 – In the introduction, ‘Cross-sectional clinical, demographic and serological data of the HCW at study inclusion has been presented elsewhere [20]’. Would a brief description be appropriate here?

2 – in results, figure 3 – could the assay cut-offs be added to graphs to clearly depict positivity/negativity? One anti-S negative (orange) appears to have a higher anti-S IgG read out than some of the anti-S positives.

4 – The symbols and colours use in the figures could possibly be improved to make the data more accessible.

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Reviewer #1: No

Reviewer #2: No

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SARS-CoV-2 induces a durable and antigen specific humoral immunity after asymptomatic to mild COVID-19 infection

PONE-D-21-27419R1

Dear Dr. Thålin,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Etsuro Ito

Academic Editor

PLOS ONE